let the devil out

Verb

let the devil out (third-person singular simple present lets the devil out, present participle letting the devil out, simple past and past participle let the devil out)

1. To ward off bad luck.
   • After fifteen minutes you had to pierce a hole in the back of each shell, to let the devil out and the sauce in', and then you had to rinse them clean in the water in which they had boiled.1994, Louis De Bernières, Captain Corelli's Mandolin
   • The baby yelled heartily at that event, prompting Grandma Ella van Heemstra to quote the Dutch maxim, “A good cry at the christening lets the devil out!”2001, Barry Paris, Audrey Hepburn
2. To behave badly or cause to behave badly.
   • He paused a moment to let logic sink in. Then he let the devil out. “You don't, I'm gonna punch you in the face, piss in your lobby, and shit in your kitchen..."2009, Barry Pollack, Forty-Eight X: The Lumeria Project
   • In other words, he does everything to break the shell of artificial niceness, politenes and emotional sterility of Dave's life. He deliberately makes him angry. He deliberately lets the devil out.2013, Helena Bassil-Morozow, The Trickster in Contemporary Film, page 57